In most cases, regaining weight represents a change in behavior, and it usually begins about a year after surgery. At this point, patients have become more tolerant of larger quantities of food and can eat many of the high-calorie or sugary foods that they ate before surgery. Those who start to regain weight are probably not complying with the eating habits they were taught and have reduced their physical activity. Patients who succeed in maintaining their weight loss continue to eat appropriately and remain physically active.

For patients who have the adjustable gastric band, weight regain usually means that the band needs to be tightened. However, band erosion may be at the root of a loss of restriction and weight gain. Patients who abused their pouch by chronically overeating may also have developed a concentric pouch dilatation. After gastric bypass, the ability to eat larger portions of food is normal, but it may expand the pouch and widen the passageway between the pouch and intestine. When that happens food moves out of the pouch faster and increases appetite. In either case, the patient should go back to their surgeon for an evaluation.